DMPA is a hormonal birth control method that is given as an injection. It is not known if taking DMPA together with anti-HIV drugs changes the amount of DMPA and/or the amount of anti-HIV drugs in the blood. If higher levels of DMPA occur, side effects may increase. If lower levels of anti-HIV drugs occur, the drugs may become less effective against HIV. This study will look at the levels of anti-HIV drugs and DMPA in the blood when these medications are used together.